Changed my Battery, increased MPG by 10%

[VX_Arky]

The original battery that came with my Toyota 4Runner lasted 7 years. I thought that was pretty darn good, but you've got me smoked!!!

[theclencher]

Yeah, 5-8 or so years is all I usually get too, although I am over 10 years on an Interstate motorcycle battery too. I don't know what makes the Motorcraft so special. The truck must have the perfect charging voltage, the battery must have the perfect design and high quality materials, and I must have the perfect use pattern.

[BamZipPow]

Disconnecting the battery could've reset the ECU which means it could be learning yer current driving habits vs the previous owner's habits...

[Jay2TheRescue]

Originally Posted by bowtieguy

actually it can...my wife's camaro had some sensor issues during a low battery situation. it was confirmed by a data stream read out before and after a new battery install. apparently the computer was not getting enough "juice" to read, communicate, and diagnose accurately.

I had a similar problem on my 81 Buick years ago. There was an internal short to ground in one of the sensors. I figured it out because all the trouble codes thrown at me were sensors coming off the 5 volt reference on the CPU. I had to reset the computer and drive the car with one sensor unplugged at a time till I got the right one, and then I only had one code. Took a couple of days to figure out that one.

[bowtieguy]

you mean i could have saved myself the cost of a new battery?!

seriously tho, the battery was on it's way out. besides, i think replacing a battery before it fails is good maintenance...especially for your wife's car. i think the married guys know what i mean

[theholycow]

Originally Posted by BamZipPow

Disconnecting the battery could've reset the ECU which means it could be learning yer current driving habits vs the previous owner's habits...

Good point. Not only does it relearn your driving but it relearns its sensors, which may have changed a little from aging.

Originally Posted by bowtieguy

especially for your wife's car. i think the married guys know what i mean

This man speaks the truth.

I roll with questionable batteries in my own vehicles, but I make sure my wife has a good battery.

[chriswf]

Originally Posted by theholycow

Perhaps a worn-out battery can lose efficiency, wasting more energy than a new one does during charge/discharge. If so, the alternator would have to do extra work, which of course is more drag on the engine.

However, 10% sounds quite severe. Do you have a fuel log with well-controlled accurate fill habits and a consistent route to rule out as many other variables as possible?

Hold on guys, I've actually had a similar situation to this. I had a battery that was dying if the car wasn't driven for a couple of days (89 civic wagon). The battery was just weak and crap. I swapped in a new battery and the lights got brighter and my mpg probably went up by at least 2 or 3, and this was mid winter. So climate can't be blamed.

After that I later pulled a sub box out of the back, wiring, amp, and more... All around lost about 150-200lbs of weight and gained another 2-3mpg, and even less strain on the alternator --- returning the car to factory condition. Even though I was at EPA with weight and bad battery... My city/hw mpg passed the EPA average(?) by 4-6mpg after weight and alternator stress lifted.

[1cheap1]

My mileage was degrading, when i popped the hood i found that the battery terminals where covered in green crap. Cleaned them up, oil and filter change and am running smooth as before. I will see after i get through this next tank. Battery is still good.

[imzjustplayin]

I charged and equalized the battery in the Volvo I'm driving and I found a 10% increase in my fuel economy. I think there really is something to having a fully charged battery. Charging the battery can help but if the battery cells are unequal as was the case with me, then equalizing them should help. I plan to get a battery desulphater to see if I can improve the battery's cranking amps.

[add|ct]

^Interesting, I know my battery is somewhat low on fluid currently, it looks to have sweated some recently(possibly from the alternator having to run at full-recharge from jumping it off a while back now, 3-4 months). I never re-checked the fluid level under the caps, but did put it on a slow charge overnight about a month after the initial 'headlights left on for 2-3 hours bit'.

FWIW, this Civic calls for a 51R, and it currently has a 51 installed. Of course, the battery cables are connected to the correct post, but still makes me wonder.